762x39 154-grain soft-point _VS_ .308 fmj 150grain


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jlott00
January 5, 2010, 10:59 PM
another noob question

will a 154 grain 762x39 have the same power as a .308 150 grain?

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rizbunk77
January 5, 2010, 11:01 PM
I don't think it would even be close. Especially if one is allowed to compare handloads.

hogshead
January 5, 2010, 11:05 PM
39 vs 51 dont think so

Maverick223
January 5, 2010, 11:18 PM
In a word...No!

The sissy little 7.62x39 154gr. has a velocity of about 2100fps, thus giving it about 1500ft/lbs of energy.

OTOH the mediocre 7.62x51 (or rather the .308Win.) 150gr. has a velocity of about 2900fps, thus giving it about 2700ft/lbs of energy.

...And the much manlier .300WM 150gr. has a velocity of up to 3300fps, thus providing a generous 3600ft/lbs of energy.

So in short...they lied...size does matter. :D

memphisjim
January 5, 2010, 11:21 PM
ok i think you asked your question wrong
im assuming you mean stopping power of the 7.62x39mm vs a fmj in a 308
id say that within 300 yards the softpoint bullet will do more damage to a flesh target

Maverick223
January 5, 2010, 11:27 PM
ok i think you asked your question wrong...im assuming you mean stopping power of the 7.62x39mm vs a fmj in a 308
id say that within 300 yards the softpoint bullet will do more damage to a flesh targetIn that case I agree, the FMJ will have more "power" (or energy), but less energy deposited into the target (will punch a clean hole, and energy spent going through a neighboring tree doesn't count), and a smaller diameter hole (barring tumbling, fragmentation, et cetera), creating a smaller permanent cavity and perhaps a smaller temporary cavity as well...and have LESS "stopping power" than the soft point with less energy...UNLESS you are trying to stop a Buick. :D

jlott00
January 5, 2010, 11:37 PM
well ill admit...i dont understand "grain" size's.....

i thought a 154 grain x39 would have the same power as a 150 grain x51 in a smaller bullet.....again im a noob..sorry

hogshead
January 5, 2010, 11:40 PM
They both shoot the same diameter bullet . The 308 has more case capacity meaning it pushes the same size bullet faster.

elmerfudd
January 5, 2010, 11:48 PM
The 154 or 150 refers to the bullet weight. In this case they're just about the same. The x39 and x51 refer to the length of the brass case. That means the x51 has considerably more powder driving that bullet. More powder means more velocity, which means more energy and the capability to penetrate further or do more damage.

jlott00
January 6, 2010, 12:09 AM
oh ok, makes since now...thanks

NG VI
January 6, 2010, 12:11 AM
7.62x39mm is the caliber/one of the case dimensions (length), .308 is basically identical to 7.62x51mm, it has much more horsepower than any 7.62x39, regardless of bullet weight, which is the grain number you are seeing and asking about. A .308 with a lighter bullet, like Hornady's 110, or one of the 125s, will have more power than a 154 7.62x39mm.


The 7.62x39mm is an intermediate cartridge designed for lighter, smaller rifles, while the .308/7.62x51mm is a full-power rifle round.

W L Johnson
January 6, 2010, 12:16 AM
This may help
7.62x51 is the 1st one 7.62x39 is the 2nd
Notice the longer case, 51mm vs 39mm
http://www.65grendel.com/gallery/762N_762R_65S_65G_556.jpg

Maverick223
January 6, 2010, 12:36 AM
WL, what are the third and fourth cartridges? .260Rem (with a gigantic, short ogive bullet) and 6.5Grendel?

Grain is a unit of measurement for weight, there are 7000 per pound. The measurement is used for both the measurement of the projectile and the weight of the powder charge. In this case the bullet weight is nearly identical, the powder charge is very different (more than double the powder in the .308Win.). The grain weight that is generally listed on a box of cartridges indicates the bullet weight. The formula for kinetic energy is KE=0.5MV², where M=mass and V=velocity.

:)

Shadow Man
January 6, 2010, 12:48 AM
The formula for kinetic energy is KE=MV², where M=mass and V=velocity.

Thank you Professor :D

While this seems to be a dying horse, I'll throw my hat into the ring anyway. Unequivocally, a 154gr SP in x39 will not have the same "power" as a 150gr FMJ in x51. In a soft target, the SP will have a more massive and immediate energy dump than a FMJ, but that in no way translates into more "power".

And is it just me, or does 154gr's seem a tad heavy for a x39? I don't think I've ever seen commercial loads over 130grs...but I don't look around much, just get what I need and get out.

Maverick223
January 6, 2010, 01:09 AM
Thank you ProfessorAnytime pupil. :D

And is it just me, or does 154gr's seem a tad heavy for a x39?It is a somewhat common load, and is available in commercial offerings.

:)

scythefwd
January 6, 2010, 01:23 AM
Shadowman, the x39 is slightly more powerful than the .30-30. Depending on the manufacturer of the x39, it will have a .308, .310, or possibly a .311 diameter projectile. As to bullet weight, the .30-30 handles much heavier projectiles than 150gr, so I would expect the x39 to be able to do so (subject to over pressurization and OAL of the finished cartridge). The largest load data I have for the x39 is a 150 gr, but those loads are 9k psi under max pressure from what I can tell.

NG VI
January 6, 2010, 02:05 AM
I thought the x39 was slightly less powerful than the 30-30, on account of similiar average velocities but heavier average bullets?

Maverick223
January 6, 2010, 02:13 AM
Here is a link for some relatively common 154gr. cartridges (along with a few others): Wolf 154gr. 7.62x39mm (http://www.wolfammo.com/index.php?option=com_content&task=view&id=1&Itemid=12)

I thought the x39 was slightly less powerful than the 30-30, on account of similiar average velocities but heavier average bullets?It does, even with a 150gr. it is superior by a decent margin. It throws a 150gr. projectile about 2400fps, for about 1900ft/lbs of energy. Only at much longer ranges does the spitzer of the x39 begin to catch up due to the more favorable BC.

:)

Shadow Man
January 6, 2010, 10:49 AM
Anytime pupil.

I'm not worthy, Master :bows: :D

My .30-30's are all 180grs, and my x39's are all 123/124grs. Now, my ballistic understanding is not on par with others here, but with just a cursory glance at the two rounds, I would think that loading a 180gr bullet in a x39 would drop the energy output considerably, reducing the range/penetration, thinking of the OAL of the two cartridges. So at the same time, would greater energy/penetration/range be achieved with the .30-30 by handloading 100gr bullets? (I have some 100gr bullets around here, so it's not a totally hypothetical question)

Al Thompson
January 6, 2010, 11:10 AM
Energy, yes, penetration - it depends on the bullet construction. Obviously a FMJ 100 grain bullet would out penetrate a JHP, all other factors being equal.

A popular load around here (small deer) is a 125 gr. JSP in a .30-30. I tend to favor the factory standard 170 loads in .30-30 - bit better penetration.

Shadow Man
January 6, 2010, 11:18 AM
Thank you sir. I'm not entirely sure what the construction is; I believe semi-jacketed SP, but I could be mistaken. I'd have to go dig the boxes up.

Dr. Tad Hussein Winslow
January 6, 2010, 12:19 PM
If I was wanting to put something down inside 100-150 yards, I'd take the x39 154 SP. You can get off a second shot from a semi in the time it takes you to recover from .308 recoil, and the expanding bullet is gonna be more effective even at slower velocity, or about the same.

Boba Fett
January 6, 2010, 02:14 PM
wl, what are the third and fourth cartridges? .260rem (with a gigantic, short ogive bullet) and 6.5grendel?



http://www.65grendel.com/faq.htm

7.62x51 NATO, 7.62x39 Russian, 6.5x55 Swedish, 6.5 Grendel, and .223 Remington/5.56 NATO.

Snowdog
January 6, 2010, 03:33 PM
Whoo hoo, I got all of them right. (The 6.5x55 was hinted to by the longer case length and military-esque cupro nickel jacketed bullet, that and I one an M96).

Maverick223
January 6, 2010, 06:01 PM
7.62x51 NATO, 7.62x39 Russian, 6.5x55 Swedish, 6.5 Grendel, and .223 Remington/5.56 NATO.Should have known that...the rim and slightly longer OAL is a dead give away.

:)

W L Johnson
January 6, 2010, 06:55 PM
You guys beat me to it.
Oh, and I should have posted the link to give credit were credit is due for the photo.
http://www.65grendel.com/gallery/762N_762R_65S_65G_556.jpg

-v-
January 6, 2010, 08:09 PM
On a side note Mr. Proffesor, and your pupil, both of you get an F on your energy equation! KE=1/2MV²!

However, terminal effect wise, a heavier projectile will retain more velocity at range and will penetrate more deeply than a lighter projectile, all other things being equal. Also, as I recall the bullets of the 150-grain range tend to have a higher BC than their lighter counterparts as well, so you loose less energy over distance than the lighter 122gr projectiles.

Maverick223
January 6, 2010, 11:08 PM
On a side note Mr. Proffesor, and your pupil, both of you get an F on your energy equation! KE=1/2MV²!...can't believe I left that out...and nobody else noticed. :uhoh: Thanks, it has been fixed.

:)

Shadow Man
January 6, 2010, 11:11 PM
Hey now...no ragging on the pupil here :D

I failed HS science, okay? Never was quite my thing... :barf:

Maverick223
January 6, 2010, 11:13 PM
No excuse here I excelled in mathematics, the sciences, and engineering...well until yesterday...but it was late. :uhoh:

Shadow Man
January 6, 2010, 11:18 PM
At the risk of going OT...I was a History/Athletics guy. But I did have a special place in my heart for Architecture...don't ask. :rolleyes:

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